Digital Subtraction Angiography (DSA) imaging is used in interventional medicine to diagnose vascular disease or abnormality in patients and is also used subsequent to treatment to document the effectiveness of treatment. In acquiring DSA images in the abdominal region, multiple motion fields are present. Patient respiration produces a pixel-shift or slight movement associated with the spine and posterior ribs, a slightly more pronounced pixel-shift or movement associated with the anterior ribs, and pixel movement associated with the abdominal organs and vessels that is in a different direction than the movement of the posterior and anterior ribs. Digital subtraction angiography (DSA) is a computer-aided image processing method used to enhance vasculature images in which each pixel of data acquired in an X-ray angiography procedure is digitized. DSA relies on the comparison between images taken immediately preceding an injection of a contrast bolus (mask image) and those obtained as the contrast bolus is passing through the target vessels (contrast image). The mask image is digitally subtracted from each of the contrast images resulting in the contrast-filled vessels being rendered on a display free of the background detail contained in the mask image. Additional known image processing functions for further enhancing the final images are performed to produce a series of successive images which are then replayed sequentially enabling a healthcare practitioner to visualize fluid flow through the target vessels.
A pixel-shifted DSA image is acquired by shifting an image relative to a mask (reference) image to align images in a DSA image sequence so that they are aligned to the background within the mask image to improve visualization of contrast enhanced structures. However artifacts arise in processing multiple individual images if one or more individual images exhibit shifts in contrast enhanced structures in a different direction than that of the background i.e. multiple different motion induced shifts occur in a single image.
Known linear pixel-shift systems typically account for one motion field, dependant on the region of interest (ROI) to which the pixel-shift is applied. If a ROI encompasses bones, the bones are shifted in each image to align with a mask image and the vessels are not aligned with each other and are positioned in each subtracted image in a different position. This results in an inferior result when producing a multiple image composition comprising pixel-shifted DSA images. In known systems additional motion applied to contrast enhanced structures impedes evaluation or compositional review of multiple images. A system according to invention principles addresses these deficiencies and associated problems.